1. Field of Invention
This invention is directed to completion, production, or injection trees for producing oil and gas from a subsea well and is specifically directed to cone seal valve means and connector for vertical access to a capless production tree for workover.
2. Prior Art
U.S. Pat. No. 4,607,701 to Gundersen, U.S. Pat. No. 4,497,369 to Hurta et al, U.S. Pat. No. 4,219,223 to Schulte, U.S. Pat. No. 4,460,156, U.S. Pat. No. 3,321,217 to Ahlstone, U.S. Pat. No. 4,440,423 to Pfeifler, U.S. patent application Ser. No. 727,658, filed 04/26/85 by Albert and Dean and U.S. patent application Ser. No. 805,028, filed 12/04/85 by Seehausen.
A typical prior art completion tree is equipped to be locked onto the wellhead of a subsea well and comprises essentially a series of valves and their actuators, for connecting production and other tubing within the well to subsea flowlines which bring the well production to the production platform or to shore. A tree manifold at the top of the tree provides a junction point for all hydraulic control functions and interfaces with a tree cap during production and with a running tool during installation of the tree and re-entry to the well for workover. Both the tree cap and running tool direct the flow of hydraulic fluid (control signals) to various valve actuators, the flowline connector and the wellhead connector, etc. The number of valve actuators in the tree depends upon; the tubing program, whether or not the tree is to be a through flowline (TFL) type, whether or not access to the annulus is to be provided, and whether or not special features are required, such as chemical injection, etc. The Hurta et al Patent discloses a control system through the tree manifold and tree cap as an example thereof.
In this prior art completion tree, it is the tree cap that directs the hydraulic control signals from a bundle of control lines, (umbilical) connected to the tree cap and to various valve operators.
During production, the tree cap, and normally the tree cap protector, are in place on the manifold and production is out the side of the tree to the subsea flowlines.
If re-entry to the well for workover is desired, the running tool is lowered to remove the tree cap protector and tree cap and after bringing them to the surface, is again run and stabbed on the tree manifold to control the tree actuators from the surface to perform whatever work is necessary to the well.
A disadvantage of the prior art system is that when a tree cap is removed from the tree manifold and before the running tool can be landed, sea water intrusion and contamination of control circuits can result. Also, during periods when neither the tree cap nor the running tool are connected to the tree manifold, the completion tree is completely divorced from the surface and is thus out of control. Further, the number of running operations involving costly rig time for workover access to the tree.
This disadvantage was overcome by providing the top block of a tree with valve cartridges mounted on a valve plate, in lieu of a tree cap, to perform the functions of a tree cap and thus eliminate the need for a tree cap in the Gundersen patent.